It's not just how we are raised. It's also the "me first" society we are in today. Liberalism teaches " you have rights!" And to hell with responsibilities or the feelings or rights of others.
Why do you think we have people shooting others if they feel "dissed" by someone? Or the road rage that ends up with someone dead?
It's a "hooray for me, and screw you" world.
I have had the same thing at the library.
Try speaking up to the librarian about it, and tell the kids to "knock it off!" When they make noise at the computers. You have the right to silance when you are there.
If that doesn't work, take a pair of ear plugs with you.
I don't blame you for being frustrated.